In business situations, non-porous surfaces are often used for presentations. Especially, transparent sheets of plastic film are often used in conjunction with overhead projectors to enable a large group of people to visually perceive written information. These transparent sheets are commonly termed transparencies. Useful in marking on such non-porous surfaces are markers and pens containing inks, crayons, and sufficiently soft pencils of various colors. However, it is often difficult to highlight information on such non-porous surfaces as transparencies.
One method of highlighting or identifying especially important information is to indicate the information in a color differing from the color of the general text or image. Changing the color of a mark is not readily done with the coloring instruments such as those described. Generally, highlighting has been accomplished in the past by merely holding over writing or attempting to cover over one color with a second color. When performing such highlighting, the marks produced are often not the desired color or clarity and the tips of the markers get soiled with the other inks, further reducing the effectiveness of the highlighting. Therefore, there has been a long felt need for compositions, including inks, and markers containing such compositions, which produce marks of a first color that can be readily changed into a wide variety of second colors. Especially needed is such a group of compositions which may be used in markers without soiling the nib of the second used marking instrument.
Coloring compositions generally are mixtures of a coloring matter dispersed or dissolved in a carrier fluid. The colorant, if readily dissolving in the carrier fluid, is termed a dye. An insoluble coloring material is termed a pigment. Pigments are finely ground solid materials and the nature and amount of pigment contained in an ink determines its color.
In one available marker application, a child is able to change a specific initial mark laid down to a second specific color by applying a reducing agent to the first mark yielding a change in color. The marker inks used in these markers are typically prepared by blending a reducing agent (sometimes termed a bleaching agent) or pH sensitive dye with a dye that is stable in reducing agent or high pH. For example, German Patent Specification No. 2724820, (hereinafter "the German Patent"), concerns the combining of a chemically stable dye and a chemically unstable dye in an ink formulation. Once a mark using this combination of stable and unstable dyes is laid down, the mark may be overwritten with a clear reducing agent solution, eliminating the color contribution of the unstable dye. The resulting mark of the stable dye, with its characteristic color, remains.
There are several drawbacks to such a marking system. First, there are strict limitations on the number of color changes which may be produced. Specifically, in formulations made according to the German Patent, the particular ink composition may only be changed from a first color to a fixed second color. For example, a green mark may only be changed to a violet color as the inks are described in the practice of the German Patent. In addition, since one of the required pair of markers contains only the reducing agent, that reducing agent marker cannot render a visible mark and may only be used in combination with the base color marker. Once the base color marker is used up, the reducing agent marker is of no use. Or, once the reducing agent marker is used up, the base color marker may only be used for the color which it initially marks with. A further disadvantage of the marking process of the German Patent is that the nib of the reducing agent marker tends to get soiled by picking up the colors of the base coloring composition, thus tainting the color of subsequent marks.
Coloring composition may also optionally include such ingredients as humectants, preservatives, and drying agents. Humectants function to improve freeze/thaw stability and to control drying out of the tip when the coloring composition is used as a marker ink. Preservatives serve the obvious function of preventing spoilage of the ink during the expected shelf life of the marker product. Drying agents speed drying of a mark laid down by a marker.
Therefore, an object of the present invention is to provide a coloring composition system which is capable of enhanced multiple color changing abilities for use on non-porous surfaces.
An additional object of the present invention is to produce a coloring composition system which includes at least two different coloring compositions each of which may be used independently or which may be used in combination to provide color changing ability on non-porous surfaces.
A further object of the present invention is to provide a coloring composition system in the form of inks for use on non-porous surfaces which prevents a nib of a color changing marker from becoming visibly soiled from contacting a base color composition.
These and other objects will become apparent to those skilled in the art to which the invention pertains.